The instant invention relates to thermal color printers and more particularly to a three-pass thermal dye transfer color printer with a continuous web print media.
Three-pass thermal color printers utilizing a continuous web of print media have heretofore been known in the art. In this regard, the U.S. Pat. No. to Nozawa et al U.S. Pat. No. 5,021,804; Fiscella et al U.S. Pat. No. 5,270,735; and Fiscella U.S. Pat. No. 5,218,380 represent the closest prior art to the subject invention of which the Applicant is aware.
The basic printing arrangement as taught by the prior art is illustrated in simplified form in prior art FIG. 1. A three-pass thermal color printer prints three separate primary colors in overlapping relation onto a thermal print media 10 to achieve a single full color image. In this connection, a roll 12 of transfer film 14 is provided with sequential sets of colored panels, i.e. Yellow, Magenta, Cyan, Yellow, Magenta, Cyan, etc. In each of the prior art printing device cited above, the primary drive rollers 16 are situated downstream of the printhead 18, i.e. the printhead 18 is situated between the roll of print media 10 and the drive rollers 16 so that the print media 10 is drawn through the printhead 18 from the continuous web. In most cases a cutter mechanism 20 is provided at the outlet of the printing device for separating the printed section of the print media from the continuous web. In operation of the prior art printing devices, the drive rollers 16 draw the print media 10 through the printhead 18 in the direction of arrow 22 to print the first color. The printhead 18 is then lifted and the drive rollers 16 reverse to push the print media 10 backwardly in the direction of arrow 24 to its starting position in preparation for printing the next color in overlapping relation. The printhead 18 is lowered, the dye ribbon 14 advanced to the next color panel, and then the drive rollers 16 again draw the print media 10 through the printhead 18 to print the second color. The process is repeated for the third color to achieve a full color print. The print media 10 is then advanced outwardly of the printer and severed by the cutter mechanism 20 at cut line 26.
While the prior art printing devices are effective for producing high-quality color images, it has been found that there is a significant amount of print media 10 wasted for each image that is printed and separately removed from the printer, i.e. when the printer is used for single image, or one-up instant issue printing. When the prior art printers are used in single image printing, they effectively waste a length of print media equal to the distance between the print line 28 of the printhead 18 to the cutter mechanism 20 each time an image is printed. In reality, this can translate into several inches of wasted print media for each printed image removed from the printer.
The instant invention provides a three-pass thermal dye transfer color printer for printing a color image on a continuous web of print media which overcomes the media waste problems of the prior art printers. The instant thermal printer comprises a thermal print station comprising a thermal printhead and an associated printhead platen. The printhead has an upstream side positioned adjacent the roll of print media and an opposite downstream side. The thermal printer further comprises a set of drive rollers positioned between the printhead and the roll of print media. The drive rollers are operative for drawing the print media through the printhead in an upstream direction, i.e. toward the roll of print media, and advancing the print media in a downstream direction. In operation, the drive rollers draw the print media in an upstream direction whereby the printhead prints an image on the print media starting from a mid-point on the print media to the terminal end thereof. The drive rollers then advance the print media in a downstream direction so that the next printing operation can be overlayed onto the first printed image. The printer reciprocates the print media back and forth until three separate color images are overlayed to achieve a full color image. The drive rollers are further operative for advancing the print media in a downstream direction to eject the printed image form the printer. By reversing the orientation of the printhead and reversing the direction of printing, the instant printer effectively eliminates all wasted print media when the printed image is severed from the continuous web.
Accordingly, it is an object of the instant invention to provide a three-pass thermal dye transfer color printer with a continuous web of print media which does not waste print media.
It is another object to provide a three-pass thermal color printer which has a reversed direction of print.
It is still another object to provide a three-pass thermal color printer which is simple is design, easy to assemble, and inexpensive to manufacture.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.